1. Field of the Invention
The present invention relates to an image recording apparatus which allows adjustment of image density by controlling image formation conditions in accordance with the density of an original image.
2. Description of the Prior Art
In a conventional image recording apparatus such as an electronic copying machine, methods are adopted wherein the density of an original image is detected by an image sensor such as a phototransistor and the light quantity for original exposure is controlled in accordance with the detected density, or the surface potential of the original image on a photosensitive body is detected by a surface potentiometer and the light quantity for original exposure and development bias are changed in real time.
However, from the viewpoints of sensitivity stability or charging characteristic stability of the photosensitive body, these methods have a drawback of unstable copy density for an original of the same density. Furthermore, depending upon the original, the reproduced image may have an irregular density in the scanning direction.
When the original density is read, the peak value of the density of the background of the original may be read, and the image formation conditions such as exposure or development bias may be changed according to the detected peak value. In this case, if an original is a document which only has two gray levels corresponding to characters and background, a clear copy may be automatically obtained. However, with a halftone image such as a photograph, a copy of only a few gray levels may be obtained.